great plains

Too Many Bison | Earth Wise

September 21, 2023 By EarthWise Leave a Comment

In the northern part of Yellowstone National Park, an historically large bison herd is hampering the comeback of quaking aspen trees, whose numbers were greatly diminished by decades of over-browsing by elk. Restoring the balance of ecosystems at Yellowstone is proving to be a complicated matter.

Long ago, the bison population in the Great Plains was as much as 30 million. The population sharply decreased in the 1800s. By the 1830s, there were no bison east of the Mississippi River. Fifty years later, the Plains bison was nearly extinct. Several small herds lived near Yellowstone Park when it was established in 1872, but poachers killed off nearly of them by the turn of the century. Protective measures were taken and by 1925, Yellowstone’s Lamar Valley herd had grown to more than 750. After that, occasional culling took place for over 40 years.

When gray wolves and cougars were removed from the park, elk populations boomed, and the elk gradually decimated the growth of quaking aspen, cottonwood, willow, and berry-producing shrubs. Both elk and bison were regularly culled until 1968 when public and congressional outcry intervened.

The return of wolves and cougars to the park made some progress in restoring ecosystem balance, particularly with respect to the elk population which has dropped from 20,000 to 5,000. But bison numbers have grown to over 4,000 over past 20 years and the damage once caused by elk is now continuing from bison.

Park administrators are faced with complex management decisions about how to best preserve the ecosystems at Yellowstone National Park.

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Bison in northern Yellowstone proving to be too much of a good thing

Photo, posted October 6, 2016, courtesy of Christian Collins via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Hot July | Earth Wise

August 24, 2022 By EarthWise Leave a Comment

At the beginning of July, the National Oceanic and Atmospheric Administration’s monthly climate outlook predicted temperatures well above average across much of the United States. The prediction was quite correct. Beyond that, world-wide, there were multiple heat waves, especially in Europe and Asia, where there were thousands of heat-related deaths. On July 19th, the United Kingdom had its hottest day ever reported with a temperature over 104 degrees.

In the U.S., a series of atmospheric high-pressure systems resulted in stagnant heat domes, which resulted in more than 150 million people living under heat warnings and advisories. Nearly every part of the continental U.S. saw above-average temperatures. There were record-breaking triple-digit highs in several states, sometimes persisting for days.

The south-central part of the country developed a ridge of high pressure that established a heat dome that acted like a lid, trapping hot air over that area. The extreme heat persisted throughout the month, at times expanding to the Southwest, Upper Midwest, and Southeast.

In the second half of the month, the Great Plains experienced temperatures as high as 115 degrees. Utah and Oklahoma both broke long-standing records for the most consecutive days on which temperatures exceeded 100 degrees. Utah saw 16 straight days over 100.

In the Pacific Northwest temperatures reached 110 degrees in Dallasport, Washington, and 114 in Medford, Oregon. In the Northeast, Newark, New Jersey saw a record-breaking five straight days over 100 degrees.

In Albany, New York, where the average daily high temperature is 82 degrees in July, there were 10 days in the 90s, with highs of 97 on three occasions.

July was a hot month indeed.

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A July of Extremes

Photo, posted July 10, 2022, courtesy of Dominic Alves via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Too Many Bison | Earth Wise

May 8, 2020 By EarthWise Leave a Comment

The population of large herbivores in Yellowstone National Park has undergone many dramatic changes over the course of time. The numbers of both the iconic Rocky Mountain elk and bison have gone up and down as a result of human interactions.

Bison, of course, once were a dominant species from east of the Appalachians to west of the Rocky Mountains, with most of an estimated 30 million living on the Great Plains. As the west was settled, bison populations plummeted and by the late 1800s, they were nearly extinct.

When Yellowstone was established, there were exactly 22 bison in the park. By 1925, there were more than 750 in the park and culling of the herd in the park’s Lamar Valley was practiced for the next four decades.

The elimination of predators like grey wolves and cougars in the early 1900s caused both elk and bison populations to mushroom and both underwent culling. When culling was ended in 1968, there were 4,000 elk and 100 bison. Within 20 years, those numbers were 20,000 and 1,000. Reintroducing wolves and cougars reduced the elk population to about 5,000, but bison numbers have continued to grow, now reaching about 4,000.

While the long-term recovery of the Yellowstone bison herd is a major conservation success story, the fact is that bison are powerful ecosystem engineers. Large numbers of them disrupt species distribution across scrub steppe and grasslands because of what they eat, trample, and rub their horns and bodies on. They have a tremendous capacity to limit the structure and composition of ecosystems.

Park administrators have complicated management decisions to make to take into account the often wide range of ecological effects that abundant large herbivores can have on ecosystems.

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Bison in northern Yellowstone proving to be too much of a good thing

Photo, posted August 10, 2016, courtesy of Brian Gratwicke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Shifting Ecosystems

August 29, 2019 By EarthWise Leave a Comment

The Great Plains ecosystem has been shifting northward over the past fifty years, driven by climate change, wildfire suppression, energy development, land use changes, and urbanization. The ecosystem is an area historically rich with grasslands and shrub steppe and is prime habitat for grassland birds.

According to a recent study published in the journal Nature Climate Change, the northernmost ecosystem boundary of the Great Plains has moved more than 365 miles north since 1970, amounting to about 8 miles a year. The region’s southernmost ecosystem boundary has shifted 160 miles north, or about 4 miles a year.

The study used bird distribution data as an indicator of shifting ecosystem boundaries. The researchers analyzed 46 years of data for 400 bird species across a 250-mile-wide strip stretching from Texas to North Dakota. They tracked how the birds’ distributions changed as a measure of how these ecosystems were shifting.

While climate change has been a major driver of these ecosystem shifts since the 1970s, several other factors such as wildfire trends, land use changes, and invasion of tree species into grassland habitat have also played a role. Like most things in ecological systems, the changes are likely to have multiple causes. One cannot really separate causes like tree invasions, warming climate, and wildfires, as they are all interrelated.

Using bird distribution patterns for tracking ecosystem shifts could be a useful tool for scientists and land managers in the coming decades to give them an early warning of how habitats are changing in response to rising global temperatures and therefore allow them to take action to protect vulnerable species.

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Great Plains’ Ecosystems Have Shifted 365 Miles Northward Since 1970

Photo, posted March 24, 2017, courtesy of Rick Bohn / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Cold Weather In A Warming Climate

June 25, 2018 By EarthWise Leave a Comment

The climate is warming. The average global temperature is going up year after year, bringing about significant changes to weather around the world. But the fact is that these changes don’t always lead to warmer weather. And ordinary variations in local weather can also go in either direction.

The Incredible Shrinking Bison

April 18, 2016 By WAMC WEB

As the climate warms, all sorts of things are happening in the environment. We know about shrinking ice caps, retreating glaciers, strange winter weather, and so forth. But there are other things that may happen that are unexpected and puzzling.